Stents are generally cylindrical-shaped devices that are radially expandable to hold open a segment of a vessel or other anatomical lumen after implantation into the body lumen.
Various types of stents are in use, including expandable and self-expanding stents. Expandable stents generally are conveyed to the area to be treated on balloon catheters or other expandable devices. For insertion, the stent is positioned in a compressed configuration along the delivery device, for example crimped onto a balloon that is folded or otherwise wrapped about a guidewire that is part of the delivery device. After the stent is positioned across the lesion, it is expanded by the delivery device, causing the diameter to expand. For a self-expanding stent, commonly a sheath is retracted, allowing expansion of the stent.
Stents may be used in conjunction with a graft. When the graft is used to deliver drugs or other therapeutic agents for medical therapeutic applications, 100% coverage of the portion of the vessel in direct contact with the graft is possible. The graft component of a stent graft may also aid in minimizing thrombosis, preventing embolic events, and minimizing contact between the fissured plaque and the hematological elements in the bloodstream.
In addition, the graft component makes the device suitable for use in treating aneurysms. An aneurysm is a bulge or sac that forms in the wall of a blood vessel. The force of normal blood pressure in the aneurysm may cause the vessel to rupture. Aneurysms result from many causes that weaken the vessel wall, including but not limited to heredity, trauma, or disease.
A number of methods and devices have been developed for treating aneurysms. A standard treatment is surgery, which is performed to bypass the section of the vessel where the aneurysm has formed. Some patients are not good candidates for such open surgery, and, due to the highly invasive nature of the open procedure, other patients may not wish to undergo the treatment.
An alternative treatment is a technique known as endovascular stent grafting. In this procedure, a stent graft is placed inside the vessel affected by the aneurysm to bypass the weakened vessel wall, thereby preventing rupture of the aneurysm. Like stents, stent grafts are delivered to the area to be treated using balloon catheters or other expandable devices and may deliver one or more therapeutic agents.
Placing stent grafts at the ostia of vessels has been difficult due to placement restrictions—placing a stent graft at an ostium requires that the stent graft be close to but not overlapping the ostium to maintain the desired blood flow between the main vessel and a branch vessel. Another approach is to provide a fenestration in the side of a graft at the branching ostium, in some instances, a branching tube to seal to the branch has been proposed. An exemplary approach is disclosed by Wisselink in U.S. Pat. No. 6,428,565. However, the Wisselink reference requires customizing the stent graft to correspond to the vessel anatomy ensuring the seal between the graft devices.
Therefore, it would be desirable to have a stent graft system that overcomes the aforementioned and other disadvantages.